
class ArithmeticUtils<T>{
  T removeNull( T para){
    if(para is Map){
      para.removeWhere((key, value){
        if(value is List<Map<String,dynamic>>){
          for(Map<String,dynamic> item in value){
            item.removeWhere((key, value) => value == null);
          }
        }
        if(value is Map<String,dynamic>){
          value.removeWhere((key1, value1) => value1 == null);
          return false;
        }
        if(value == null){
          return true;
        }
        return false;
      });
      return para;
    }else if(para is List<dynamic>){
      para.remove(null);
    }
    return para;
  }
}